In some wireless networks, an access point (AP) can be coupled to a variety of wireless network devices. Typically, a wireless network can allow a mobile device to send and receive data as it moves through coverage zones of the individual access points. Sometimes, the wireless network device will initiate a session with a particular gateway. The data that is transferred to the wireless network device is sent to the gateway, which then relays the data to the wireless network device. Relatedly, the data emanating form the wireless network device is sent to the initial gateway, from where it is relayed to the ultimate destination.
When the wireless network device is mobile, the wireless network device can leave the coverage zone of a particular access point, or associated gateway. The wireless network device reinitiates contact with an access point that services the new location where the wireless network device is now located. In this manner, a new gateway may be used for the communication of information to and from the wireless network device.
In many cases, a link between the old gateway and the new gateway is established. Data traffic to the wireless network device is received by the old gateway, encapsulated by the old gateway, and relayed to the new gateway. At the new gateway, the data is decapsulated, and sent to the wireless network device.
Data traffic from the wireless network device is handled in much the same way. Data from the wireless network device is relayed from the wireless network device to the current gateway. The current gateway encapsulates the data and relays it to the original gateway. At this point, the original gateway decapsulates the data and relays it to the ultimate destination.
This paradigm is used for ongoing sessions, as well as new sessions. Thus, when the wireless network device starts a link at the new location, the encapsulation and relaying of the data from the new gateway to the original gateway is undertaken.
In this manner, a single gateway acts as the central point for all communications to and from a particular wireless network device. The transferring of the data to a new gateway takes additional time and effort, especially when the wireless network device is operating with several open sessions.
Such a mechanism may be found in the use of Mobile IP, a proposal before the Internet Engineering Taskforce (IETF). Mobile IP involves the use of a “Home Agent”, which is the location of the device's known IP address, and a “Foreign Agent”, which knows the actual location of the device. All traffic intended for the device is sent to the Home Agent and is then “tunneled” to the Foreign Agent for delivery to the device. This same type of method can be used within a wireless LAN, without the need to use the Mobile IP protocol.
In a more trivial implementation of a tunneling system to achieve seamless subnet roaming, an administrator could be forced to assign a “Home” Gateway for each wireless user in the network. Each wireless client would then communicate to its currently local access point, which would “tunnel” the packet to the client's “Home” Gateway. However, this implementation has two major inefficiencies. First, it requires the administrator to setup a Home Gateway for each user. Secondly, and more difficult to work around, it is rather inefficient, forcing more traffic to be tunneled than necessary.